The production of algal biomass has increasingly been of interest. The potential usage of such material is found across a wide range of applications, including biofuel feedstock production, fertilizer, nutritional supplements, pollution control, and other uses.
For example, various approaches such as “open-air” and “closed-air,” have been considered for mass production of algal biomass. The United States Department of Energy conducted a program called the Aquatic Species Program from 1978 to 1996. The engineering efforts of the program were largely focused on large “open-air” racetrack pond designs. The ponds are so-named based on the fact that the culture medium is conveyed in a complete circuit in a continuous fashion. This flow of culture medium is achieved with large continuously turning paddle wheels, which induce a turbulent flow in the medium. The turbulent flow is necessary to mix the culture so that all algae cells receive sunlight. The ponds are similar in appearance to extremely elongated ovals.
Although such “open-air” approaches are generally effective, shortfalls exist. For example, such systems risk incursion of invasive species, which can severely hamper growth of the desired algae. Evaporation of culture medium leading to large demands on water resources is a significant issue. In addition, such open-air approaches are not as effective as closed systems in sequestration of carbon dioxide emissions.
“Closed-air” systems generally refer to systems that contain algal biomass production within a controlled environment, limiting exposure to outside air. Examples of such systems include closed photo-bioreactor structures forming a closed container for housing a culture medium for generating algal biomass. Having a controlled environment helps maximize the generation of algal material by limiting exposure to invasive species as well as controlling other environmental factors that promote algal growth. Closed-air systems significantly reduce evaporation and therefore significantly reduce demands on water resources. In addition, closed-air systems facilitate the sequestration of carbon dioxide gas, which promotes algal growth, facilities compliance with environmental regulations, and benefits the environment generally.
Accordingly, such closed-air systems are beneficial in many respects. However, such systems can be expensive and, in many instances, cost prohibitive. One of the main areas of cost for algal photo-bioreactors is the reactor material itself. Clear glass or acrylic tubes cost so much that the economic value of the biomass generated within the reactor over its lifetime may not be high enough to pay for the reactor itself.
Lightweight plastic film has been used as an alternative structure for providing a container for housing a culture medium. Such plastic film structures are comparatively inexpensive to set up, however, such material is much more prone to degradation, particularly from extended exposure to solar radiation. Current implementations that use such materials typically result in an effective useful lifetime between about one to two years. Thus, considering such a short lifespan, cost effectiveness of such structures is questionable.
It should be appreciated that there remains a need for a system and method of generating algal biomass in an efficient and cost-effective manner. The present invention fulfills this need and others.